Type II alcoholism is characterized by early onset heavy drinking, risk taking, and violence which are commonly described as impulsive behaviors. This subtype of alcoholism has been demonstrated to be highly heritable, transmittable primarily from father to son. There is also considerable evidence suggesting that neurochemical substrates may underlie this condition. In particular, numerous studies have demonstrated that impaired serotonergic functioning correlates with the described impulsive behaviors associated with Type II alcoholism. The overall aim of this project is to examine the link between impulsivity and serotonergic dysfunction in young men at high risk for Type II alcoholism. In a controlled laboratory environment, using double blind, placebo controlled conditions, central nervous system serotonin levels will be manipulated by depleting plasma tryptophan stores. The effects of these manipulations on behavior will be examined using several standardized, performance based measures of impulsivity. It is predicted that individuals at high risk for Type II alcoholism will be more sensitive to the effects of serotonin depletion than low risk individuals as indicated by their performance on the impulsivity measures. Using laboratory procedures to examine the relationship between serotonin deficiency and impulsivity in high risk subjects will add validity to the serotonergic theory of Type II alcoholism.